1. Field of the Invention
The present invention relates to processing performed to remove an abnormality on a data communication line, and to a printing process for the transmission of data along, for example, an IEEE 1394 line.
2. Related Background Art
Since for the performance of a communication process across a so-called centronics line only an image data source and a printer are connected together, basically, even when a physical line is disconnected, the canceling of a session is not required unless a user physically breaks the connection. And when data are being transmitted to other apparatuses, if a lower layer is disconnected from a line, accordingly an upper layer is immediately disconnected from the line.
Assume that, as provided for by the IEEE 1394 specification, a plurality of image data sources and a plurality of printers are connected together along a single, closed communication line. If, for example, one of the image sources that is connected to the line and that is transmitting data is disconnected, and if a printer that during a session communicates with that image data source continues to be connected to the source, as with a centronics line, the printer will be unable to transmit data to other image data sources on the line.
If an upper layer is disconnected immediately after a lower layer is disconnected, or if the disconnection and the re-connection of a line is performed due to the careless performance of an operation by a user or due to a rearrangement of apparatuses, the printing process must be repeated from the beginning. As a result, an undesirable, excessive expenditure of time, paper and ink (toner, etc.) occurs.